1. Field of the Invention
The present invention relates to a digital broadcasting receiving device, and particularly to a digital broadcasting receiving device having a viewing restriction function.
2. Description of Related Art
In United States and Canada, a regulation requires that television sets which receive television broadcast signals must have a V-chip allowing a viewer to restrict reception and display of improper video and sound of violence scenes and obscene images which are desired not to be watched by children. Specifically, with a conventional V-chip defined by CEA-766-A, each television set stores a rating region table (hereinafter, referred to as “fixed RRT”) which includes predetermined TV rating and MPAA rating, and viewing restriction is applied based on the fixed RRT.
However, in order to change or expand the rating region table, the Federal Communications Commission has required since Mar. 15, 2006 that a digital television broadcasting receiving device having the size of 13 inch or more include a V-chip 2.0. With the V-chip 2.0, the digital television broadcasting receiving device can recognize a rating region table (hereinafter, referred to as “variable RRT”) sent during broadcasting and apply program viewing restriction.
Also, with the V-chip 2.0, rating information of each program is sent together with the broadcast signal in the same way as with the conventional V-chip, and viewing restriction is applied based on a combination of the rating information and the fixed RRT or the variable RRT.
As a technique of using rating information in the conventional V-chip, JP 2003-198974 A discloses a technique in which the rating information of a channel being tuned is accumulated in association with program titles or the like to allow a user to refer to the rating information upon rating setting. Further, JP 2003-518881 A discloses a technique of obtaining, while one channel is being viewed, the rating information of another channel for the purpose of preventing a reduction in the speed of channel zapping caused by rating-information acquisition and decision processing. Further, JP 2003-110953 A discloses a technique of applying viewing restriction based on rating information for multiple days that is sent together with an EPG, to prevent a program to which viewing restriction should be applied from being displayed during a period of time required for rating-information acquisition and decision processing immediately after channel switching.
A device for receiving television broadcasting has a channel map that associates the number of each physical channel specified by a user through a key operation with the number of each logical channel assigned to the frequency band of a broadcast signal. In the channel map, if the number of a logical channel is not assigned to the number of a physical channel, video is not displayed even when the user selects that physical channel. However, when the user performs a key operation, the user expects some video to be displayed.